This invention relates to a diagnostic system for microbial identification. More particularly, it relates to a process for the identification of Neisseria species, especially N. gonorrhoeae and N. meningitidis. It further relates to the reagents for use in the process and to apparatus for carrying out the process, including a test strip made of a number of small receptacles or reaction chambers each containing a synthetic substrate and a buffer and being adapted to contain a test inoculum during incubation.
The incidence of gonorrhea has reached epidemic proportions. About three million cases of gonorrhea occurred in the United States during 1975. A system for the rapid identification of N. gonorrhoeae will be a major aid in the identification of the infection and the subsequent treatment of the patient. The term "gonorrhea" encompases all infections caused by the gonococcus Neisseria gonorrhoeae.
The increased isolation of N. gonorrhoeae from nongenital sites, as well as the isolation of N. meningitidis and N. lactamica from genital sites presents a problem in the clinical laboratory. All of these species of Neisseria will grow on media used for the isolation of N. gonorrhoeae. Therefore, isolates must be further characterized to ascertain the identity of the organism.
The conventional techniques for the identification of N. gonorrhoeae require the culturing of a specimen on a selective medium followed by an ozidase test, a gram stain and a morphology study to make a presumptive identification of N. gonorrhoeae.
Confirmation of the identification by conventional techniques requires further incubation on a non-selective enrichment medium, such as a chocolate agar plate, to obtain sufficient growth for the confirmatory tests. Incubation for 18 to 24 hours is required to obtain sufficient growth. The growth from the foregoing medium is inoculated to carbohydrate degradation medium which usually consists of a battery of the carbohydrates: glucose (dextrose), maltose, sucrose, fructose, levulose and lactose sugars in cystine-trypticase agar base with phenol red indicator. They are incubated in aerobic conditions as required for carbohydrate degradation for up to two days during which time the carbohydrates may be converted into acidic end products. The presence of acid is detected by the change in color of an indicator, such as phenol red, from red to yellow, which indicates a positive reaction. The conventional technique for confirmation can require up to three days.
Some processes are known for a more rapid identification of N. gonorrhoeae. The known rapid processes utilize a primary isolation on a selective medium, as in the conventional technique, followed by inoculation of a primary isolation plate to grow the inoculum. The carbohydrate degradation media are then inoculated with a very dense suspension of the bacteria and incubated in a water bath for up to 5 hours to produce an acid reaction. That is, they use a small amount of the substrate, and a very dense bacteria suspension and accelerate the reaction. The processes do not depend on the growth of the organism under these conditions but depend on the presence of preformed enzyme that will degrade the various substrates.